diff --git a/oracle/callees.go b/oracle/callees.go
index 1e0d65e1..a9ee1890 100644
--- a/oracle/callees.go
+++ b/oracle/callees.go
@@ -41,8 +41,10 @@ func callees(o *Oracle, qpos *QueryPos) (queryResult, error) {
 	}
 
 	// Reject calls to built-ins.
-	if b, ok := qpos.info.TypeOf(call.Fun).(*types.Builtin); ok {
-		return nil, o.errorf(call, "this is a call to the built-in '%s' operator", b.Name())
+	if id, ok := unparen(call.Fun).(*ast.Ident); ok {
+		if b, ok := qpos.info.ObjectOf(id).(*types.Builtin); ok {
+			return nil, o.errorf(call, "this is a call to the built-in '%s' operator", b.Name())
+		}
 	}
 
 	buildSSA(o)
diff --git a/ssa/builder.go b/ssa/builder.go
index 045b7a4b..58eb0015 100644
--- a/ssa/builder.go
+++ b/ssa/builder.go
@@ -265,15 +265,15 @@ func (b *builder) exprN(fn *Function, e ast.Expr) Value {
 }
 
 // builtin emits to fn SSA instructions to implement a call to the
-// built-in function called name with the specified arguments
+// built-in function obj with the specified arguments
 // and return type.  It returns the value defined by the result.
 //
 // The result is nil if no special handling was required; in this case
 // the caller should treat this like an ordinary library function
 // call.
 //
-func (b *builder) builtin(fn *Function, name string, args []ast.Expr, typ types.Type, pos token.Pos) Value {
-	switch name {
+func (b *builder) builtin(fn *Function, obj *types.Builtin, args []ast.Expr, typ types.Type, pos token.Pos) Value {
+	switch obj.Name() {
 	case "make":
 		switch typ.Underlying().(type) {
 		case *types.Slice:
@@ -554,9 +554,8 @@ func (b *builder) expr0(fn *Function, e ast.Expr) Value {
 		}
 		// Call to "intrinsic" built-ins, e.g. new, make, panic.
 		if id, ok := e.Fun.(*ast.Ident); ok {
-			obj := fn.Pkg.objectOf(id)
-			if _, ok := fn.Prog.builtins[obj]; ok {
-				if v := b.builtin(fn, id.Name, e.Args, typ, e.Lparen); v != nil {
+			if obj, ok := fn.Pkg.objectOf(id).(*types.Builtin); ok {
+				if v := b.builtin(fn, obj, e.Args, typ, e.Lparen); v != nil {
 					return v
 				}
 			}
@@ -639,7 +638,7 @@ func (b *builder) expr0(fn *Function, e ast.Expr) Value {
 	case *ast.Ident:
 		obj := fn.Pkg.objectOf(e)
 		// Universal built-in?
-		if obj.Pkg() == nil {
+		if obj, ok := obj.(*types.Builtin); ok {
 			return fn.Prog.builtins[obj]
 		}
 		// Package-level func or var?
@@ -1750,7 +1749,7 @@ func (b *builder) rangeIndexed(fn *Function, x Value, tv types.Type) (k, v Value
 	} else {
 		// length = len(x).
 		var c Call
-		c.Call.Value = fn.Prog.builtins[types.Universe.Lookup("len")]
+		c.Call.Value = fn.Prog.builtins[types.Universe.Lookup("len").(*types.Builtin)]
 		c.Call.Args = []Value{x}
 		c.setType(tInt)
 		length = fn.emit(&c)
diff --git a/ssa/create.go b/ssa/create.go
index 47e51160..fb6de474 100644
--- a/ssa/create.go
+++ b/ssa/create.go
@@ -43,7 +43,7 @@ func NewProgram(fset *token.FileSet, mode BuilderMode) *Program {
 		Fset:                fset,
 		imported:            make(map[string]*Package),
 		packages:            make(map[*types.Package]*Package),
-		builtins:            make(map[types.Object]*Builtin),
+		builtins:            make(map[*types.Builtin]*Builtin),
 		boundMethodWrappers: make(map[*types.Func]*Function),
 		ifaceMethodWrappers: make(map[*types.Func]*Function),
 		mode:                mode,
@@ -51,7 +51,7 @@ func NewProgram(fset *token.FileSet, mode BuilderMode) *Program {
 
 	// Create Values for built-in functions.
 	for _, name := range types.Universe.Names() {
-		if obj, ok := types.Universe.Lookup(name).(*types.Func); ok {
+		if obj, ok := types.Universe.Lookup(name).(*types.Builtin); ok {
 			prog.builtins[obj] = &Builtin{obj}
 		}
 	}
diff --git a/ssa/source.go b/ssa/source.go
index f490a323..8f539128 100644
--- a/ssa/source.go
+++ b/ssa/source.go
@@ -178,18 +178,13 @@ func (prog *Program) packageLevelValue(obj types.Object) Value {
 	return nil
 }
 
-// FuncValue returns the SSA Value denoted by the source-level named
-// function obj.  The result may be a *Function or a *Builtin, or nil
-// if not found.
+// FuncValue returns the Function denoted by the source-level named
+// function obj.
 //
-func (prog *Program) FuncValue(obj *types.Func) Value {
-	// Universal built-in?
-	if v, ok := prog.builtins[obj]; ok {
-		return v
-	}
+func (prog *Program) FuncValue(obj *types.Func) *Function {
 	// Package-level function or declared method?
 	if v := prog.packageLevelValue(obj); v != nil {
-		return v
+		return v.(*Function)
 	}
 	// Interface method wrapper?
 	meth := recvType(obj).MethodSet().Lookup(obj.Pkg(), obj.Name())
diff --git a/ssa/source_test.go b/ssa/source_test.go
index fc72290f..366aac0e 100644
--- a/ssa/source_test.go
+++ b/ssa/source_test.go
@@ -103,28 +103,19 @@ func TestObjValueLookup(t *testing.T) {
 }
 
 func checkFuncValue(t *testing.T, prog *ssa.Program, obj *types.Func) {
-	v := prog.FuncValue(obj)
-	// fmt.Printf("FuncValue(%s) = %s\n", obj, v) // debugging
-	if v == nil {
+	fn := prog.FuncValue(obj)
+	// fmt.Printf("FuncValue(%s) = %s\n", obj, fn) // debugging
+	if fn == nil {
 		t.Errorf("FuncValue(%s) == nil", obj)
 		return
 	}
-	// v must be an *ssa.Function or *ssa.Builtin.
-	v2, _ := v.(interface {
-		Object() types.Object
-	})
-	if v2 == nil {
-		t.Errorf("FuncValue(%s) = %s %T; has no Object() method",
-			obj, v.Name(), v)
-		return
-	}
-	if vobj := v2.Object(); vobj != obj {
+	if fnobj := fn.Object(); fnobj != obj {
 		t.Errorf("FuncValue(%s).Object() == %s; value was %s",
-			obj, vobj, v.Name())
+			obj, fnobj, fn.Name())
 		return
 	}
-	if !types.IsIdentical(v.Type(), obj.Type()) {
-		t.Errorf("FuncValue(%s).Type() == %s", obj, v.Type())
+	if !types.IsIdentical(fn.Type(), obj.Type()) {
+		t.Errorf("FuncValue(%s).Type() == %s", obj, fn.Type())
 		return
 	}
 }
diff --git a/ssa/ssa.go b/ssa/ssa.go
index 2610eadc..d80098a6 100644
--- a/ssa/ssa.go
+++ b/ssa/ssa.go
@@ -25,7 +25,7 @@ type Program struct {
 	Fset     *token.FileSet              // position information for the files of this Program
 	imported map[string]*Package         // all importable Packages, keyed by import path
 	packages map[*types.Package]*Package // all loaded Packages, keyed by object
-	builtins map[types.Object]*Builtin   // all built-in functions, keyed by typechecker objects.
+	builtins map[*types.Builtin]*Builtin // all built-in functions, keyed by typechecker objects.
 	mode     BuilderMode                 // set of mode bits for SSA construction
 
 	methodsMu           sync.Mutex                // guards the following maps:
@@ -401,12 +401,14 @@ type Global struct {
 // Builtins are immutable values.  Builtins do not have addresses.
 // Builtins can only appear in CallCommon.Func.
 //
-// Type() returns a *types.Builtin.
-// Built-in functions may have polymorphic or variadic types that are
-// not expressible in Go's type system.
+// Object() returns a *types.Builtin.
+//
+// Type() returns types.Typ[types.Invalid], since built-in functions
+// may have polymorphic or variadic types that are not expressible in
+// Go's type system.
 //
 type Builtin struct {
-	object *types.Func // canonical types.Universe object for this built-in
+	object *types.Builtin // canonical types.Universe object for this built-in
 }
 
 // Value-defining instructions  ----------------------------------------